Cell-cell interactions are fundamental to the survival of a multi-cellular organism. Control and diagnosis of normal and abnormal cell-cell interactions is important in all areas of human health ranging from embryonic development and immune function to uncontrolled tumor growth in cancer and infectious disease. Our long-term goal is the development of defined polymer systems that can be used for activation, inhibition, and discovery of cell-surface receptors to unravel these complex cell-cell interactions. Our objectives in this proposal are 1) to develop mimics of the zona pellucida moieties that initiate the sperm acrosome reaction and which may be used to identify the sperm zona pellucida receptors;2) to develop methods to identify extracellular receptors that are in low abundance;and 3) to develop alternating polymer structures that will advance our understanding of biology. Our hypothesis is that control of functional group spacing, backbone flexibility, and functional group variability in polymer synthesis will provide a powerful, molecular approach to elucidate cell-cell interactions. We expect to establish the appropriate mixture and density of sugars for optimally activating the sperm acrosome reaction and to develop a general method for isolating and identifying components of membrane-bound receptor complexes. Further development of alternating ring-opening metathesis polymerization chemistry will provide long, linear polymers for displaying alternating functional groups and will enable application of the methods developed in this work to the study of cell-cell interaction in a wide variety of biological systems.